0026529: CMake offers rebuilding of platform dependent code unclear for an user

0026529: CMake offers rebuilding of platform dependent code unclear for an user

Fix for building with GCC and CLang

CMake variable descriptions updated
"Building with CMake" article updated

BuildToolkit.cmake cleaned up and renamed
"TestCases" project and all relating variables removed; custom script added for building environment
DrawAppliInit is copied from occt root to CMake binary dir if the file exists

rebuild platform dependent code by cmake cleaned up
Flex & Bison compiler flags added

RelWithDebInfo OCCT libraries are moved to libi folder; the binary is moved to bini one

CMAKE_BUILD_TYPE is set as Release by-default for a single-configuration generator

env.bat in installation folder has default value of CASDEB that equals to the build type of the last installed OCCT libraries

"building with CMake" article updated